Back to EveryPatent.com
| United States Patent |
5,264,174
|
|
Takei
, et al.
|
November 23, 1993
|
Process for producing compositely reinforced polypropylene resin
composition
Abstract
According to the present invention, there is provided a process for stably
producing a compositely reinforced polypropylene composition having less
warpage deformation and good moldability which includes the steps of using
an extruder having at least three feed inlets, feeding an organic peroxide
and a polypropylene resin selected from (a) a polypropylene modified by
grafting an unsaturated organic acid thereonto, (b) a mixture of the
resulting modified polypropylene and an unmodified polypropylene, (c) a
mixture of an unsaturated organic acid and an unmodified polypropylene or
(d) mixtures of the foregoing to the extruder through the first feed inlet
of the extruder, feeding the lamellar inorganic filler thereto through the
second feed inlet disposed at a position where the resin mixture is
sufficiently melted and kneaded, feeding the glass fiber through the third
feed inlet, and then melting and kneading these materials.
| Inventors:
|
Takei; Hiroshi (Ichihara, JP);
Yonaiyama; Rikio (Ichihara, JP);
Yoshimitsu; Minoru (Ichihara, JP);
Atsumi; Nobukazu (Ichihara, JP)
|
| Assignee:
|
Mitsubishi Denki Kabushiki Kaisha (Tokyo, JP)
|
| Appl. No.:
|
955033 |
| Filed:
|
October 1, 1992 |
Foreign Application Priority Data
| Current U.S. Class: |
264/211.23; 264/211; 524/449; 524/494 |
| Intern'l Class: |
C08K 005/14 |
| Field of Search: |
524/449,494
264/211,211.23,331.17
523/348
|
References Cited
| Foreign Patent Documents |
| 3520151 | Dec., 1986 | DE | 264/328.
|
| 59-105042 | Jun., 1964 | JP.
| |
| 52-36141 | Mar., 1977 | JP.
| |
| 55-40719 | Mar., 1980 | JP.
| |
| 58-206659 | Dec., 1983 | JP.
| |
| 60-23432 | Feb., 1985 | JP.
| |
| 64-11218 | Feb., 1989 | JP.
| |
Primary Examiner: Hoke; Veronica P.
Attorney, Agent or Firm: Leydig, Voit & Mayer
Claims
What is claimed is:
1. A process for producing a compositely reinforced polypropylene resin
composition containing at least 10% by weight of a glass fiber and at
least 20% by weight of a lamellar inorganic filler and having a melt flow
rate of at least 10 g/10 minutes (230.degree. C., 10 minutes and a load of
2.16 kg) comprising the steps of feeding, using an extruder having at
least three feed inlets, an amount of organic peroxide sufficient to
shorten molecular chains and a polypropylene resin selected from the group
consisting of (a) a polypropylene modified by grafting an unsaturated
organic acid thereonto, (b) a mixture of said modified polypropylene and
an unmodified polypropylene, (c) a mixture of an unsaturated organic acid
and an unmodified polypropylene, and (d) mixtures of the foregoing to the
extruder through the first feed inlet of the extruder, feeding the
lamellar inorganic filler thereto through the second feed inlet disposed
at a position where the resin mixture is sufficiently melted and kneaded,
feeding the glass fiber thereto through the third feed inlet, and then
melting and kneading these materials.
2. The process for producing a compositely reinforced polypropylene resin
composition according to claim 1 wherein the lamellar inorganic filler is
mice.
3. The process for producing a compositely reinforced polypropylene resin
composition according to claim 1 wherein a mixture of a polypropylene
modified by grafting an unsaturated organic acid thereonto, an unmodified
polypropylene, and an organic peroxide is fed to the extruder through the
first feed inlet of the extruder.
4. The process for producing a compositely reinforced polypropylene resin
composition according to claim 1 wherein a mixture of an unsaturated
organic acid, an unmodified polypropylene, and an organic peroxide is fed
to the extruder through the first feed inlet of the extruder.
5. The process for producing a compositely reinforced polypropylene resin
composition according to claim 4 wherein the amount of unsaturated organic
acid is in the range of about 0.01 to 5% by weight, based on the weight of
the unmodified polypropylene.
6. The process for producing a compositely reinforced polypropylene resin
composition according to claim 3 wherein the amount of unsaturated organic
acid is in the range of about 0.01 to 5% by weight, based on the total
weight of modified and unmodified polypropylene.
7. The process for producing a compositely reinforced polypropylene resin
composition according to claim 1 wherein the amount of lamellar inorganic
filler is about 20 to about 45% by weight, based on the weight of the
resin composition.
8. The process for producing a compositely reinforced polypropylene resin
composition according to claim 1 wherein the amount of glass fibers is
about 10 to about 35% by weight, based on the weight of the resin
composition.
9. A process for producing a compositely reinforced polypropylene resin
composition containing at least 10% by weight of a glass fiber and at
least 20% by weight of a lamellar inorganic filler and having a melt flow
rate of at least 10 g/10 minutes (230.degree. C., 10 minutes and a load of
2.16 kg) comprising the steps of feeding, using an extruder having at
least three feed inlets, an amount of organic peroxide sufficient to
improve flowability of the polypropylene resin composition and a
polypropylene resin selected from the group consisting of (a) a
polypropylene modified by grafting an unsaturated organic acid thereonto,
(b) a mixture of said modified polypropylene and an unmodified
polypropylene, (c) a mixture of an unsaturated organic acid and an
unmodified polypropylene, and (d) a mixture of the foregoing to the
extruder through the first feed inlet of the extruder, feeding the
lamellar inorganic filler thereto through the second feed inlet disposed
at a position where the resin mixture is sufficiently melted and kneaded,
feeding the glass fiber through the third feed inlet, and then melting and
kneading these materials.
10. The process for producing a compositely reinforced polypropylene resin
composition according to claim 9 wherein the lamellar inorganic filler is
mica.
11. The process for producing a compositely reinforced polypropylene resin
composition according to claim 9 wherein a mixture of a polypropylene
modified by grafting an unsaturated organic acid thereonto, an unmodified
polypropylene, and an organic peroxide is fed to the extruder through the
first feed inlet of the extruder.
12. The process for producing a compositely reinforced polypropylene resin
composition according to claim 9 wherein a mixture of an unsaturated
organic acid, an unmodified polypropylene, and an organic peroxide is fed
to the extruder through the first feed inlet of the extruder.
13. The process for producing a compositely reinforced polypropylene resin
composition according to claim 12 wherein the amount of unsaturated
organic acid is in the range of about 0.01 to 5% by weight, based on the
weight of the unmodified polypropylene.
14. The process for producing a compositely reinforced polypropylene resin
composition according to claim 11 wherein the amount of unsaturated
organic acid is in the range of about 0.01 to 5% by weight, based on the
total weight of modified and unmodified polypropylene.
15. The process for producing a compositely reinforced polypropylene resin
composition according to claim 9 wherein the amount of lamellar inorganic
filler is about 20 to about 45% by weight, based on the weight of the
resin composition.
16. The process for producing a compositely reinforced polypropylene resin
composition according to claim 9 wherein the amount of glass fibers is
about 10 to about 35% by weight, based on the weight of the resin
composition.
17. A process for producing a compositely reinforced polypropylene resin
composition containing at least 10% by weight of a glass fiber and at
least 20% by weight of a lamellar inorganic filler and having a melt flow
rate of at least 10 g/10 minutes (230.degree. C., 10 minutes and a load of
2.16 kg) comprising the steps of feeding, using an extruder having at
least three feed inlets, at least 0.01% by weight of an organic peroxide
and a polypropylene resin selected from the group consisting of (a) a
polypropylene modified by grafting an unsaturated organic acid thereonto,
(b) a mixture of said resulting modified polypropylene and an unmodified
polypropylene, (c) a mixture of an unsaturated organic acid and an
unmodified polypropylene, and (d) a mixture of the foregoing to the
extruder through the first feed inlet of the extruder, feeding the
lamellar inorganic filler thereto through the second feed inlet disposed
at a position where the resin mixture is sufficiently melted and kneaded,
feeding the glass fiber through the third feed inlet, and then melting and
kneading these materials.
18. The process for producing a compositely reinforced polypropylene resin
composition according to claim 17 wherein the lamellar inorganic filler is
mica.
19. The process for producing a compositely reinforced polypropylene resin
composition according to claim 17 wherein a mixture of a polypropylene
modified by grafting an unsaturated organic acid thereonto, an unmodified
polypropylene, and an organic peroxide is fed to the extruder through the
first feed inlet of the extruder.
20. The process for producing a compositely reinforced polypropylene resin
composition according to claim 17 wherein a mixture of an unsaturated
organic acid, an unmodified polypropylene, and an organic peroxide is fed
to the extruder through the first feed inlet of the extruder.
21. The process for producing a compositely reinforced polypropylene resin
composition according to claim 20 wherein the amount of unsaturated
organic acid is in the range of about 0.01 to 5% by weight, based on the
weight of the unmodified polypropylene.
22. The process for producing a compositely reinforced polypropylene resin
composition according to claim 17 wherein the amount of unsaturated
organic acid is in the range of about 0.01 to 5% by weight, based on the
total weight of modified and unmodified polypropylene.
23. The process for producing a compositely reinforced polypropylene resin
composition according to claim 17 wherein the amount of lamellar inorganic
filler is about 20 to about 45% by weight, based on the weight of the
resin composition.
24. The process for producing a compositely reinforced polypropylene resin
composition according to claim 17 wherein the amount of glass fibers is
about 10 to about 35% by weight, based on the weight of the resin
composition.
Description
BACKGROUND OF THE INVENTION
(i) Field of the Invention
The present invention relates to a process for producing a polypropylene
resin composition which has excellent mechanical strength and stiffness
and good dimensional stability and moldability and which is compositely
reinforced by a glass fiber and a lamellar inorganic filler.
(ii) Description of the Prior Art
A polypropylene resin composition reinforced with a glass fiber is
excellent in chemical resistance and has a higher reinforcing effect as
compared with compositions reinforced with another particle filler or
lamellar inorganic filler. In the polypropylene resin composition
containing 10% by weight or more of the glass fiber, strength and
stiffness are particularly high, and so this kind of polypropylene resin
composition is used in many fields as a useful industrial material.
However, the polypropylene resin composition reinforced with only glass
fiber has the drawback that molded articles obtained therefrom have large
warpage deformation.
In order to remove this drawback, Japanese Patent Publication No. 64-11218
and Japanese Patent Application laid-open No. 58-206659 disclose the
following three processes (1) to (3) which comprise quantitatively feeding
a glass fiber and a lamellar inorganic filler to the polypropylene,
melting, kneading and extruding it to compositely reinforce it.
(1) A process which comprises first melting, kneading and extruding a
mixture of a polypropylene, an organic peroxide and an unsaturated organic
acid to obtain the polypropylene (hereinafter abbreviated to "modified PP"
on occasion) on which the unsaturated organic acid is grafted, mixing this
modified PP with predetermined amounts of a lamellar inorganic filler and
a glass fiber, and then melting, kneading and extruding the mixture again.
(2) A process which comprises feeding a mixture of a modified PP and a
lamellar filler to an extruder through the first feed inlet of the
extruder on an upstream side, and then melting, kneading and extruding the
mixture while a glass fiber is fed to the extruder through the second feed
inlet of the extruder on a downstream side. The extruder for use in this
process is equipped with the second feed inlet through which the other raw
materials are fed to a position where the modified PP can be sufficiently
melted.
(3) A process which comprises quantitatively feeding the modified PP alone
through the first feed inlet on the upstream side of an extruder, and then
melting, kneading and extruding the mixture, while a glass fiber and a
lamellar inorganic filler are fed through the second feed inlet of the
extruder on the downstream side.
However, in the process in which the mixture of the modified PP, the glass
fiber and the lamellar inorganic filler or the mixture of the modified PP
and the lamellar inorganic filler is fed through one feed inlet as in the
above-mentioned processes (1) and (2), the viscosity of the resin
noticeably increases in the melting step of the resin, so that a screw in
the extruder is extraordinarily worn, with the result that the continuous
production is practically impossible. In addition, bridges are formed in
the vicinity of the feed inlet, and the composition of the product changes
by classification, and in consequence, the stability of the production is
very poor.
Furthermore, in the above-mentioned process (3), there is no problem, when
small amounts of the glass fiber and the lamellar inorganic filler are
used. However, when both the raw materials are fed in large quantities,
the bridges are formed in the vicinity of the feed inlets. In consequence,
the precision of the quantitative feed lowers, so that surging and the
breakage of strands often take place. In particular, it is substantially
impossible to continuously produce a polypropylene resin composition
containing 10% by weight or more of the glass fiber and 20% by weight or
more of the lamellar inorganic filler.
In all of the above-mentioned processes (1), (2) and (3), the composition
change noticeably occurs owing to classification in a hopper of the
extruder, so that the product having non-uniform composition can be merely
obtained. Particularly, in the case of the process (1), the strength of
the product significantly deteriorates owing to the breakage of the glass
fibers.
Next, reference will be made to a relation between the melt flowability and
the dimensional stability of the polypropylene resin composition
compositely reinforced with the glass fiber and the lamellar inorganic
filler.
In general, when the glass fiber and the lamellar inorganic filler are used
at high concentrations in the polypropylene, the melt viscosity of the
composition increases, and the flowability, i.e., melt flow rate
(hereinafter abbreviated to "MFR" on occasion) of the composition
noticeably decreases. When the composition having MFR of less than 10 g/10
minutes is injection-molded, the pressure in a mold lowers at the time of
the molding, even if a fairly large injection pressure is applied. In
consequence, the moldability of the composition deteriorates, with the
result that the effect of warpage inhibition is outstandingly impaired.
Furthermore, as a result of the extreme deterioration of the flowability,
the resin does not flow to the edges of the mold and is very poor in
moldability, unless the injection pressure and the molding temperature in
the molding step are increased.
In order to prevent this deterioration of the flowability, it is required
to substantially increase the MFR of the modified PP which is the matrix
resin. However, when the modified PP having the extremely high MFR is
manufactured by means of an extruder, the strands are often cut owing to
the shortage of melt tension and the strands fuse to each other, so that
productivity declines.
SUMMARY OF THE INVENTION
In view of such situations, an object of the present invention is to
provide a process for stably and inexpensively producing a compositely
reinforced polypropylene resin composition containing 10% by weight or
more of a glass fiber and 20% by weight or more of a lamellar inorganic
filler, having an MFR of 10 g/10 minutes or more (230.degree. C., 10
minutes and a load of 2.16 kg), excellent strength, stiffness and
moldability as well as less warpage deformation.
The present inventors have made investigation in order to solve the
above-mentioned problems, and as a result, they have succeeded in
obtaining a desired compositely reinforced polypropylene resin composition
by using an extruder having three feed inlets, feeding a specific resin
mixture to the extruder through the first feed inlet of the extruder,
feeding a lamellar inorganic filler thereto through the second feed inlet,
feeding a glass fiber thereto through the third feed inlet, and then
melting and kneading these materials. In consequence, the process of the
present invention has been completed.
That is, the present invention is directed a process for producing a
compositely reinforced polypropylene resin composition containing 10% by
weight or more of a glass fiber and 20% by weight or more of a lamellar
inorganic filler and having a melt flow rate of 10 g/10 minutes or more
(230.degree. C., 10 minutes and a load of 2.16 kg) which comprises the
steps of using an extruder having three feed inlets, feeding a
polypropylene modified by grafting an unsaturated organic acid thereonto
(a modified PP), a mixture of the modified PP and an unmodified
polypropylene, or a mixture of an unsaturated organic acid, an unmodified
polypropylene and an organic peroxide, to the extruder through the first
feed inlet of the extruder, feeding the lamellar inorganic filler thereto
through the second feed inlet disposed at a position where the resin
mixture is sufficiently melted and kneaded, feeding the glass fiber
thereto through the third feed inlet, and then melting and kneading these
materials.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an illustrative view of a co-rotating twin screw extruder (A)
having three feed inlets.
FIG. 2 is an illustrative view of a co-rotating twin screw extruder (B)
having two feed inlets.
1 . . . First feed inlet
2 . . . Second feed inlet
3 . . . Third feed inlet
4 . . . Vent
5 . . . Die
6 . . . Kneading disk
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
As an extruder for use in a process of the present invention, there can be
used a commercially available screw extruder, so long as it has three or
more feed inlets, but a co-rotating twin screw extruder is particularly
preferable. Furthermore, it is preferred that a feeder with a meter is
provided at each feed inlet to control the amount of each feed material.
No particular restriction is put on a ratio (L/D) of a length L of a
cylinder to a diameter D of a die of the extruder, but for example, in the
range of from the first feed inlet for the feed of a resin mixture to the
second feed inlet for the feed of a lamellar inorganic filler, the ratio
is 15 or more; in the range of from the second feed inlet to the third
feed inlet for the feed of a glass fiber, the ratio is 7 or more; and in
the range of from the third feed inlet to the die, the ratio is from 10 to
about 15.
When the ratio L/D in the range of from the first feed inlet to the second
feed inlet is too low, an organic peroxide does not function effectively,
and the flowability of the mixture deteriorates. Moreover, in the case
that an unsaturated organic acid is used, graft reaction is insufficient,
so that interfacial adhesive properties between the glass fiber or the
lamellar inorganic filler and a modified PP decline, with the result that
strength and stiffness of the product decrease.
The ratio L/D of from the second feed inlet to the third inlet is required
to have a value enough to sufficiently disperse the lamellar inorganic
filler, and when this ratio is too low, the glass fiber is fed to the
insufficiently dispersed lamellar inorganic filler, so that the glass
fiber is not uniformly blended, which results in the deterioration of
productivity.
Furthermore, when the ratio L/D in the range of from the third feed inlet
to the die is too low, the dispersibility of the glass fiber is poor, so
that the strength decreases, and, conversely, when the ratio is too high,
the glass fiber is broken, so that the strength decreases similarly.
In order to effectively achieve the function of the organic peroxide and to
improve the dispersion of inorganic fillers such as mica and the glass
fiber, it is preferable to employ a high-performance kneading means such
as a Dulmage screw and a kneading disk between the respective feed inlets
and between the third feed inlet and the die of the extruder.
Furthermore, for the purpose of stabilizing strands and inhibiting the
generation of air bubbles in pellets, it is preferable to dispose a vent
between the third feed inlet and the die of the extruder.
In the process of the present invention, the extrusion temperature of the
extruder is preferably in the range of from about 180.degree. to
300.degree. C., more preferably from about 200.degree. to 280.degree. C.
In the process of the present invention, the utilization effect of the
extruder can be exerted only by feeding the above-mentioned resin mixture
to the extruder through the first feed inlet on the most upstream side,
feeding the lamellar inorganic filler thereto through the second feed
inlet, and then feeding the glass fiber thereto through the third feed
inlet.
If the resin mixture, the glass fiber and the lamellar inorganic filler are
fed to the extruder through the first feed inlet, the second feed inlet
and the third feed inlet, respectively, the glass fiber is noticeably
broken at the time of melting and kneading, so that the strength of the
resultant resin composition extremely deteriorates.
Furthermore, when the mixture of the resin mixture and the lamellar
inorganic filler is fed to the extruder through the first feed inlet and
nothing is fed thereto through the second feed inlet and the glass fiber
is fed thereto through the third feed inlet, a production stability lowers
owing to the formation of bridges and the like in the vicinity of the feed
inlets, and the viscosity of the mixture of the resin mixture and the
lamellar inorganic filler noticeably increases in the melting step, so
that a screw in the extruder is outstandingly worn. Particularly, when the
lamellar inorganic filler is mica, the continuous production is
practically impossible. Additionally, in this process, the blended organic
peroxide and unsaturated organic acid are adsorbed by the inorganic
filler, before they act on the polypropylene. In consequence, there also
occurs a problem that the moldability, strength and stiffness of
composition are impaired.
Moreover, when the resin mixture is fed to the extruder through the first
feed inlet and nothing is fed thereto through the second feed inlet and
the mixture of the lamellar inorganic filler and the glass fiber is fed
thereto through the third feed inlet, bridges are easily formed in the
vicinity of the feed inlets with the accumulative increase of the fed
lamellar inorganic filler and glass fiber. In consequence, the precision
of the quantitative feed lowers, so that surging and strand breakage often
take place.
The compositely reinforced polypropylene resin composition obtained by the
process of the present invention is excellent in strength and stiffness,
and so it can be directly molded without any additional treatment. Prior
to the molding, however, the composition can be mixed with a
non-reinforced resin, i.e., unmodified polypropylene or a modified PP in
an optional ratio.
On the other hand, as a means for including the filler in the resin at a
high concentration, a melting/kneading technique using a kneader or the
like is prevalent. However, in such a technique, the breakage of the glass
fiber is perceptible, so that the excellent strength and stiffness cannot
be obtained.
The process of the present invention is only limited to the manufacture of
a compositely reinforced polypropylene resin composition containing 10% by
weight or more of the glass fiber and 20% by weight or more of the
lamellar inorganic filler and having an MFR of 10 g/10 minutes or more.
When the amount of the glass fiber to be added is less than 10% by weight,
the excellent strength cannot be obtained, and hence applications of the
products are strictly restricted. Additionally, when the amount of the
lamellar inorganic filler to be added is less than 20% by weight, the
inhibition effect of warpage deformation is noticeably impaired.
Furthermore, when the MFR of the composition is less than 10 g/10 minutes,
moldability deteriorates and the inhibition effect of the warpage
deformation is also noticeably impaired.
No particular restriction is put on the kind of lamellar inorganic filler
which is used in the process of the present invention, but examples of the
lamellar inorganic filler include mica, talc and glass flakes. Above all,
mica is particularly preferable. The amount of the lamellar inorganic
filler is 20% or more, preferably from 20 to 45% by weight based on the
weight of the resin composition.
Examples of the glass fiber which is used in the process of the present
invention include glass chopped strands and glass rovings which are
usually commercially available as additives for reinforcing resins.
Preferably, with regard to the glass fiber, an average fiber diameter is
from 5 to 20 .mu.m, and an average fiber length, in the case of the glass
chopped strands, is from 0.5 mm to 10 mm. No particular restriction is put
on the amount of the glass fiber, so long as it is 10% by weight or more,
but it is preferably in the range of from 10 to 35% by weight.
Next, reference will be made to the unmodified polypropylene, the organic
peroxide, the unsaturated organic acid and the modified PP the components
of the resin mixture for use in the process of the present invention may
be selected.
Examples of the unmodified polypropylene include a homopolymer of propylene
and block and random copolymers of propylene and one or more of
.alpha.-olefins such as ethylene, 1-butene, 1-hexene and 1-octene, etc.
No particular restriction is put on the kind of organic peroxide, but
examples include di-t-butyl peroxide, dicumyl peroxide and benzoyl
peroxide. No particular restriction is put on the amount of the organic
peroxide, but it is preferably from 0.01 to 0.5% by weight based on the
weight of the unmodified polypropylene.
Furthermore, the organic peroxide is necessary, even when either of the
unsaturated organic acid and the modified PP is used.
The organic peroxide has the effect of cutting the molecular chains of the
polypropylene to improve the flowability of the resultant resin
composition. The improvement of the flowability results in the preparation
of the resin composition having less warpage deformation and excellent
moldability. Moreover, when an unsaturated organic acid is used, the
organic peroxide permits obtaining the above-mentioned flowability and
completing the graft reaction of the unsaturated organic acid on the
polypropylene, so that the resin composition having excellent strength and
stiffness can be obtained.
No particular restriction is put on the kind of unsaturated organic acid,
but examples include unsaturated carboxylic acids and their anhydrides
such as acrylic acid, methacrylic acid, maleic acid, fumaric acid,
citraconic acid, maleic anhydride and itaconic anhydride. No particular
restriction is put on the amount of the unsaturated organic acid, but it
is preferably in the range of from 0.01 to 5% by weight based on the
weight of the unmodified polypropylene.
The modified PP can be obtained by grafting the above-mentioned unsaturated
organic acid on the unmodified polypropylene in a known suitable manner.
For example, there are a process in which a mixture of the unmodified
polypropylene, the unsaturated organic acid and the organic peroxide is
melted and kneaded, and then pelletized by the extruder, and a process in
which the above-mentioned mixture is reacted in a solvent such as xylene.
Furthermore, when the modified PP is used, the amount of the unsaturated
organic acid in the total components of the modified PP and the unmodified
polypropylene is suitably in the range of from 0.01 to 5% by weight. When
the amount of this unsaturated organic acid is less than 0.01% by weight,
the resin composition having sufficiently high strength cannot be
obtained.
In the resin mixture for use in the process of the present invention, there
can be used, if necessary, an antioxidant, an ultraviolet light absorber,
a lubricant, a silane coupling agent and the like.
When neither the modified PP nor the unsaturated organic acid is contained
in the resin mixture, good interfacial adhesion cannot be obtained between
the glass fiber or the lamellar inorganic filler and the resin, so that
the strength and stiffness of the composition largely deteriorate.
The process of the present invention can stably and inexpensively provide a
compositely reinforced polypropylene resin composition which is reinforced
with a glass fiber and a lamellar inorganic filler and which has excellent
strength, stiffness and moldability as well as less warpage deformation.
EXAMPLES
Next, the present invention will be described in detail with reference to
examples and comparative examples, but it should not be limited to these
examples.
In the examples of the present invention and the comparative examples,
evaluation was carried out by the use of extruders shown in FIGS. 1 and 2.
The extruder (A) shown in FIG. 1 is a co-rotating twin screw extruder
equipped with three feed inlets and a vent and having a bore diameter of
45 mm. A ratio (L/D) of a length L of a cylinder to a diameter D of a die
is 40 in the whole extruder, 18 in the range of from the first feed inlet
1 to the second feed inlet 2, 10 in the range of from the second feed
inlet 2 to the third feed inlet 3, and 12 in the range of from the third
feed inlet 3 to the die. Kneading disks 6 are disposed between the first
feed inlet 1 and the second feed inlet 2, between the second feed inlet 2
and the third feed inlet 3 and between the third feed inlet 3 and the die
5, respectively.
Furthermore, the extruder (B) shown in FIG. 2 is a co-rotating twin screw
extruder equipped with two feed inlets and a vent and having a bore
diameter of 45 mm. The ratio (L/D) is 30 in the whole extruder, 18 in the
range of from the first feed inlet to the second feed inlet, and 12 in the
range of from the second feed inlet to the die. The kneading disks 6 are
disposed between the first feed inlet and the second feed inlet, and
between the second feed inlet and the die, respectively.
In the examples and comparative examples, the measurement of the MFR and a
graft ratio as well as the evaluation of the resin compositions were
carried out by the following procedures.
Graft ratio
Pellets of a modified PP were dissolved in xylene at 135.degree. C., and
the resultant solution was then poured into a large amount of acetone to
precipitate a polypropylene component. Unreacted maleic anhydride was
removed therefrom, and the solution was filtered and then dried. This
dried modified PP was then subjected to infrared spectral analysis, and
grafted maleic anhydride was quantitatively analyzed from a peak at 1780
cm.sup.-1 of an infrared spectral analysis spectrum, thereby obtaining the
graft ratio.
Measurement of tensile strength (which was carried out in accordance with
JIS K7113).
Measurement of flexural modulus (which was carried out in accordance with
JIS K7203).
Measurement of MFR (230.degree. C., 10 minutes, load of 2.16 kg).
Measurement of warpage deformation (maximum warpage deformation): Test
pieces for the test were prepared by injection-molding a 2-mm-thick,
150-mm-long, 150-mm-wide plate, utilizing one whole surface thereof as a
film gate. These test pieces were conditioned at 23.degree. C. at a
relative humidity of 50% for 48 hours. Afterward, both the corners of one
side of each test piece were fixed on a horizontal base, and a distance of
the separated opposite side from the horizontal base was then measured as
the warpage deformation. However, the warpage deformation was changed by
altering the side position of each test piece which was fixed, and
therefore the measurement of the warpage deformation was carried out while
the side positions of the test piece to be fixed were changed. Of the
measured values, the maximum value was regarded as the warpage
deformation, and its unit was mm.
The resin mixtures and the modified PP which would be used in the examples
and comparative examples were prepared as follows.
(1) Resin mixture 1: This resin mixture was obtained by stirring a mixture
of 99.20% by weight of a polypropylene homopolymer powder having an MFR of
2 g/10 minutes as an unmodified polypropylene, 0.5% by weight of maleic
anhydride as an unsaturated organic acid, 0.1% by weight of
1,3-bis(t-butylperoxyisopropyl)benzene as an organic peroxide, 0.1% by
weight of 2,6-di-t-butyl-p-cresol as an antioxidant and 0.1% by weight of
calcium stearate as a lubricant for the mixer.
(2) Modified PP-2: The above-mentioned resin mixture 1 was melted and
kneaded at an extrusion temperature of 200.degree. C., and then pelletized
by the use of an extruder (B).
The thus obtained modified PP-2 had an MFR of 130 g/10 minutes and a graft
ratio of 0.3% by weight.
(3) Modified PP-3 (highly graft-modified PP): A mixture of 94.5% by weight
of a polypropylene homopolymer powder having an MFR of 2 g/10 minutes as
an unmodified polypropylene, 5.0% by weight of maleic anhydride as an
unsaturated organic acid and 0.5% by weight of
1,3-bis(t-butyl-peroxyisopropyl)benzene as an organic peroxide was reacted
at 100.degree. C. for 2 hours in xylene, and the reaction solution was
then precipitated in acetone, filtered and then dried.
The obtained modified PP had an MFR of 130 g/10 minutes and a graft ratio
of 0.3% by weight.
(4) Resin Mixture 4 (a resin mixture containing an organic peroxide and a
stabilizer only): This resin mixture was obtained by stirring a mixture of
99.70% by weight of a polypropylene homopolymer powder having an MFR of 2
g/10 minutes as an unmodified polypropylene, 0.1% by weight of
1,3-bis(t-butylperoxyisopropyl)benzene as an organic peroxide, 0.1% by
weight of 2,6-di-t-butyl-p-cresol as an antioxidant and 0.1% by weight of
calcium stearate as a lubricant for the mixer.
(5) Resin Mixture 5 (a resin mixture containing a stabilizer only): This
resin mixture was obtained by stirring a mixture of 99.8% by weight of a
polypropylene homopolymer powder having an MFR of 30 g/10 minutes, 0.1% by
weight of 2,6-di-t-butyl-p-cresol as an antioxidant and 0.1% by weight of
calcium stearate as a lubricant for the mixer.
As a lamellar inorganic filler, mica having an aspect ratio of 35 was used.
As a glass fiber, chopped strands having an average fiber length of 3 mm
and an average fiber diameter of 9 .mu.m were used. A temperature in the
extruder was set to 250.degree. C.
EXAMPLE 1
50% by weight of a resin mixture, 30% by weight of mica and 20% by weight
of a glass fiber were quantitatively fed to an extruder (A) shown in FIG.
1 through the first feed inlet, the second feed inlet and the third feed
inlet of the extruder (A), respectively. Afterward, they were melted and
kneaded under vent suction, and then pelletized.
COMPARATIVE EXAMPLE 1
The same procedure as in Example 1 was carried out except that the feed
order of a glass fiber and a lamellar inorganic filler was reversed.
COMPARATIVE EXAMPLE 2
A mixture obtained by mixing 50% by weight of modified PP-2, 20% by weight
of a glass fiber and 30% by weight of mica by a mixer was fed to an
extruder (B) shown in FIG. 2 through the first feed inlet of the extruder,
and nothing was fed thereto through the second and third feed inlets, and
the mixture was then melted and kneaded, and then pelletized under vent
suction to prepare a composition in the form of the pellets.
However, during the preparation, bridges were often formed at the feed
inlets for the raw materials, so that the raw materials were not stably
fed. Thus, the preparation process was continued, while the bridges were
removed by poking them with a resin rod. By this operation, strands were
substantially stabilized, but a little while later, surging occurred
instead. Hence, a screw was drawn and then inspected, and as a result, it
was apparent that the portion of the extruder in the vicinity of a
kneading disk was noticeably worn. Therefore, the production was stopped.
COMPARATIVE EXAMPLE 3
A mixture obtained by mixing 50% by weight of modified PP-2 and 30% by
weight of mica by a mixer was quantitatively fed to an extruder (B) shown
in FIG. 2 through the first feed inlet of the extruder, and 20% by weight
of a glass fiber were quantitatively fed thereto through the second feed
inlet. Afterward, the mixture was melted and kneaded, and then pelletized
under vent suction.
Immediately after the start of the preparation, the modified PP and mica
were classified in the first feed inlet, and strands were often cut by
surging attributed to the fluctuation of the composition. A little while
later, the surging grew vigorous and the operation became impossible, as
in Comparative Example 2. Thus, a screw was drawn and then inspected, and
as a result, it was apparent that the portion of the extruder in the
vicinity of a kneading disk was noticeably worn. Therefore, the production
was stopped.
COMPARATIVE EXAMPLE 4
70% by weight of modified PP-2 was quantitatively fed to an extruder (B)
shown in FIG. 2 through the first feed inlet of the extruder, and a
mixture obtained by mixing 10% by weight of a glass fiber and 20% by
weight of mica by a mixer was quantitatively fed thereto through the
second feed inlet. Afterward, the mixture was melted and kneaded, and then
pelletized under vent suction.
In this example, the amounts of the glass fiber and mica were less than in
the other examples, but many bridges were formed at the second feed inlet,
so that the glass fiber and mica were not stably fed and strands were
often cut. Therefore, the production was unavoidably stopped.
EXAMPLE 2
5% by weight of modified PP-3 and 45% by weight of a resin mixture 4
(including an organic peroxide and a stabilizer only) were quantitatively
fed to an extruder (A) shown in FIG. 1 through the first feed inlet of the
extruder, and 30% by weight of mica and 20% by weight of a glass fiber
were fed thereto through the second feed inlet and the third feed inlet,
respectively. Afterward, the mixture was melted and kneaded, and then
pelletized under vent suction.
COMPARATIVE EXAMPLE 5
A mixture obtained by mixing 5% by weight of modified PP-3 and 45% by
weight of a resin mixture 5 (containing a stabilizer only) by a mixer was
quantitatively fed to an extruder (A) shown in FIG. 2 through the first
feed inlet of the extruder, and 30% by weight of mica and 20% by weight of
a glass fiber were quantitatively fed thereto through the second feed
inlet and the third feed inlet, respectively. Afterward, the mixture was
melted and kneaded, and then pelletized under vent suction.
COMPARATIVE EXAMPLE 6
50% by weight of a resin mixture 4 (containing an organic peroxide and a
stabilizer only), 30% by weight of mica and 20% by weight of a glass fiber
were quantitatively fed to an extruder (A) shown in FIG. 1 through the
first feed inlet, the second feed inlet and the third feed inlet of the
extruder, respectively. Afterward, the mixture was melted and kneaded, and
then pelletized under vent suction. The results are set forth in Table 1.
EXAMPLE 3
30% by weight of a resin mixture 1, 35% by weight of mica and 35% by weight
of a glass fiber were quantitatively fed to an extruder (A) shown in FIG.
1 through the first feed inlet, the second feed inlet and the third feed
inlet of the extruder, respectively. Afterward, the mixture was melted and
kneaded, and then pelletized under vent suction. The results are set forth
in Table 1.
Raw materials feed conditions in the examples and comparative examples are
set forth in Table 1, and the evaluation results of the resin compositions
are set forth in Table 2.
TABLE 1
______________________________________
(I)
Feed Conditions of Raw Material
First Feed Inlet
Kind of Amount
Extruder
Raw Material (wt %)
______________________________________
Example 1
A Resin Mixture 1
50
Comparative
A Resin Mixture 1
50
Example 1
Comparative
B Modified PP-2 50
Example 2 Mica 30
Glass Fiber 20
Comparative
B Modified PP-2 50
Example 3 Mica 30
Comparative
B Modified PP-2 70
Example 4
Example 2
A Modified PP-3 5
Resin Mixture 4
45
Comparative
A Modified PP-3 5
Example 5 Resin Mixture 5
45
Comparative
A Resin Mixture 4
50
Example 6
Example 3
A Resin Mixture 1
30
______________________________________
TABLE 1
______________________________________
(II)
Feed Conditions of Raw Material
Second Feed Inlet
Kind of Amount
Extruder
Raw Material (wt %)
______________________________________
Example 1
A Mica 30
Comparative
A Glass Fiber 20
Example 1
Comparative
B -- --
Example 2
Comparative
B Glass Fiber 20
Example 3
Comparative
B Glass Fiber 10
Example 4 Mica 20
Example 2
A Mica 30
Comparative
A Mica 30
Example 5
Comparative
A Mica 30
Example 6
Example 3
A Mica 35
______________________________________
TABLE 1
______________________________________
(III)
Feed Conditions of Raw Material
Third Feed Inlet
Kind of Amount
Extruder
Raw Material (wt %)
______________________________________
Example 1
A Glass Fiber 20
Comparative
A Mica 30
Example 1
Comparative
B -- --
Example 2
Comparative
B -- --
Example 3
Comparative
B -- --
Example 4
Example 2
A Glass Fiber 20
Comparative
A Glass Fiber 20
Example 5
Comparative
A Glass Fiber 20
Example 6
Example 3
A Glass Fiber 35
______________________________________
TABLE 1
______________________________________
(IV)
Results of Evaluation
Tensile Flexural
Kind of
Strength Modulus
Extruder
(kg/cm.sup.2)
(kg/cm.sup.2)
______________________________________
Example 1 A 1300 120000
Comparative
A 640 62000
Example 1
Comparative
A Stable Production was impossible.
Example 2
Comparative
B Stable Production was impossible.
Example 3
Comparative
B Stable Production was impossible.
Example 4
Example 2 A 1250 118000
Comparative
A 980 95000
Example 5
Comparative
A 520 101000
Example 6
Example 3 A 1650 138000
______________________________________
TABLE 1
______________________________________
(V)
Results of Evaluation
Tensile Flexural
Kind of
Strength Modulus
Extruder
(kg/cm.sup.2)
(kg/cm.sup.2)
______________________________________
Example 1 A 30 1.5
Comparative
A 30 2.0
Example 1
Comparative
A Stable Production was impossible.
Example 2
Comparative
B Stable Production was impossible.
Example 3
Comparative
B Stable Production was impossible.
Example 4
Example 2 A 28 1.6
Comparative
A 0.5 70.0
Example 5
Comparative
A 26 2.5
Example 6
Example 3 A 15 1.0
______________________________________
As is apparent from Table 1, with regard to the product obtained in Example
1 concerning the process of the present invention, tensile strength and
flexural modulus were excellent and they were 1300 kg/cm.sup.2 and 12000
kg/cm.sup.2, respectively. Furthermore, MFR was as high as 30 g/10
minutes, and so warpage deformation was also at a good level of 1.5 mm. In
addition, after the production, wear of the screw was not observed at all,
and a stable feed condition of the raw materials was also excellent.
Comparative Example 1 is an example in which the same raw materials as in
Example 1 were used and the feed order of the glass fiber and mica was
reversed. In the case of such a feed order, MFR and warpage deformation
were not so different from those of Example 1, but since the glass fiber
was broken, tensile strength and flexural modulus deteriorated to about
half of those of Example 1.
In short, the effect of the present invention can be exerted only when the
resin mixture, the lamellar inorganic filler and the glass fiber were fed
to the extruder through the first feed inlet on the most upstream side,
the second feed inlet and the third feed inlet, respectively.
Comparative Examples 2 to 4 are examples in which conventional procedures
were used, but in all of these examples, the stable production was
difficult and so the production was stopped halfway.
Firstly, in Comparative Example 2, the bridges were formed at the raw
material feed inlets, and the raw materials could not be stably fed. In
addition, during the production, the surging occurred. Thus, a screw was
drawn and then inspected, and as a result, it was apparent that the
portion of the extruder in the vicinity of a kneading disk was noticeably
worn.
Also in Comparative Example 4, the fluctuation of the feed composition
occurred in the first feed inlet owing the classification, so that stable
production could not be achieved. In addition, the screw was noticeably
worn.
Moreover, in Comparative Example 4, the amounts of the glass fiber and mica
were 10% by weight and 20% by weight, respectively, and these amounts were
smaller than in the other examples. Nevertheless, the bridges were
outstandingly formed at the third feed inlet, so that the glass fiber and
mica could not be stably fed.
In short, the conventional process could not practically produce a
polypropylene resin composition compositely reinforced with 10% by weight
or more of the glass fiber and 20% by weight or more of the lamellar
inorganic filler.
Example 2 and Comparative Example 5 were examples for comparing the blend
effect of the organic peroxide. In these examples, the amount of the
modified PP in the matrix was equal, but in Example 2 in which the organic
peroxide was added, MFR was 28 g/10 minutes, and the warpage deformation
was 1.6 mm. On the contrary, in Comparative Example 5 in which the organic
peroxide was not added and the highly graft-modified PP was diluted with
the unmodified PP having an MFR of 30 g/10 minutes, MFR extremely
deteriorated to 0.5 g/10 minutes, so that the warpage deformation
inconveniently increased to 70 mm. In addition, tensile strength and
flexural modulus also noticeably declined.
This can be presumed to be due to the fact that even if the polypropylene
having the high MFR was used, the viscosity of the polypropylene increased
owing to the blend of the glass fiber and mica, and the breakage of the
glass fiber was inevitable.
Comparative Example 6 is an example in which the organic peroxide was only
contained in the matrix resin and neither the unsaturated organic acid nor
the modified PP was contained.
In this case, the interfacial adhesion was not present between the resin
and the fillers, and so the strength of the product was extremely low.
Example 3 is an example which succeeded in the composite packing of the
glass fiber and the lamellar inorganic filler at a high concentration, in
contrast to the conventional process.
In short, the conventional process could not practically provide the stable
production, even if the amounts of the glass fiber and the lamellar
inorganic filler were as low as in Comparative Examples 2 to 4. On the
contrary, in Example 3 utilizing the process of the present invention,
stable production was possible and wear of the screw was not observed at
all after the production, even if the amount of the glass fiber was 35% by
weight, that of mica were 35% by weight, and its total amount was 70% by
weight.
Top